A standard drill chuck has a chuck body that is normally mounted on the spindle of the drill and rotated about the axis thereof for drilling. An adjustment body normally formed as a sleeve is axially fixed but rotatable on the chuck body. One of the bodies is formed with a plurality of angularly equispaced angled guides each slidably receiving a respective jaw and teeth on these jaws mesh with a screwthread on the other body so that relative rotation of the bodies in one direction moves the jaws radially toward each other and opposite relative rotation moves them radially apart.
In order to hold the chuck in the clamping position, it is standard as described in WO 91/12,914 (U.S. equivalent U.S. Pat. No. 5,174,588) to provide a locking ring that is axially displaceable on one of the bodies and that has teeth axially meshable with teeth on the other body. A spring urges the ring axially forward to mesh the teeth together. This ring is at most limitedly rotatable on the one body so that when the teeth are engaged with each other, the bodies are locked against relative rotation. A holding ring that is rotatable on the bodies is coupled via appropriate cam formations to the locking ring so that when the locking ring is held back the holding ring can retain it in this position and thereby maintain the teeth out of mesh with each other. Thus to loosen such a chuck the locking ring is retracted and then the holding ring is turned to retain the locking ring in the retracted out-of-mesh position. The chuck is set up so that when it is tightened the holding ring is automatically rotated into the releasing position that lets the locking ring move back forward into the advanced meshed position.
Thus to operate the chuck one must separately maneuver the locking and holding rings and one of the bodies. This means that the locking and holding rings as well as one of the bodies must present sufficient surface area to grab and hold. As a result the surface of the chuck is divided into three relatively narrow bands that must be separately handled. The only way to make this construction convenient is to build the chuck relatively long, which is clearly disadvantageous in that such a tool must be fitted into confined spaces and must be as compact as possible.